The invention relates to a dowel-type device for precisely positioning a component having a through-bore relative to a reference part which also has a bore of the same inside width as the through-bore.
French Pat. No. 907,671 teaches an expanding dowel for attaching a component to a wall, in which the dowel is inserted into a blind hole in the wall and a bolt extending through a through-bore in the component engages in an expanding cone, which, by turning the bolt, presses the sides of the expanding dowel against the inside wall of the blind hole.
In order to fix a component exactly on a reference part, a high degree of accuracy is necessary. This is so especially when a workpiece is to be subjected to electric discharge machining and the permissible deviation of the actual position of the workpiece from its nominal expected position relative to the reference part should not be allowed to exceed a distance on the order of a few microns. Nevertheless, the fixing in position of the component on the reference part must be repeatable as often as necessary without loss of precision. The component itself may be a workpiece to be machined or even part of a workpiece holder. The reference part may, for example, be a work table.
The expanding dowel known from civil engineering and building construction is unsuitable for locating with the necessary repeatability and precision.